1. Field of the Invention
The present invention relates to a technique for reducing a scale of a data read circuit of a solid-state imaging device and current consumption of the data read circuit.
2. Description of the Related Art
In general, an imaging apparatus has a data read circuit provided in each column of a pixel array. The data read circuit reads a noise signal and a data signal with the noise signal superposed thereon from a pixel circuit, generates a signal (an actual data signal) from which a common mode noise is removed by a CDS (Correlated Double Sampling) circuit, and converts the generated signal, which is an analog signal, into a digital signal using an ADC (Analog to Digital (A/D) Conversion) circuit contained in the data read circuit.
In addition, Japanese Unexamined Patent Application Publication No. 2002-218324 discloses a data read circuit including a chopper type voltage comparator, a first switch connecting an input node of the chopper type voltage comparator to an output node of a pixel circuit, and a capacitor provided between the input node of the chopper type voltage comparator and an output node of a ramp signal generating circuit, for the purpose of reduction of the scale and current consumption of the data read circuit.
The data read circuit having the CDS circuit and the ADC circuit provided separately is enlarged in its scale as the number of amplifiers increases. As a result, the production costs of the data read circuit are raised. In addition, the increase of the number of the amplifiers causes the increase of the current consumption and the deterioration of data read accuracy. Moreover, since the data read circuit disclosed in Japanese Unexamined Patent Application Publication No. 2002-218324 uses the chopper type voltage comparator in which a signal is transmitted from its input side to its output side via the capacitor, it may take a long time to perform a data read operation. Therefore, such a data read circuit cannot be employed for an imaging apparatus having a number of pixels because the imaging apparatus requires a high-speed data read operation.